International Journal of Engineering and Applied Sciences (IJEAS) ISSN: 2394-3661, Volume-2, Issue-11, November 2015
Enhancement of visible light photocatalytic activity of MoO3 with V2O5 additive T. Narasimha Murthy, P. Suresh and A.V. Prasada Rao
Rhodamine-B, Methylene blue, Methyl orange and Eosin Y. The present study is taken up to explore whether addition of V2O5 because of its lesser band gap compared to MoO3 will enhance the efficiency of MoO3 towards photocatalytic degradation of Rhodamine-B (Rh-B), Methylene blue (MB), Methyl orange (MO) and Eosin-Y (EY).
Abstract— Both MoO3 and V2O5 exhibit considerable absorption in the visible region as seen from their UV-visible diffuse reflectance spectra. In view of higher absorption of V2O5 compared to MoO3, the present study is tken up to see whether addition of V2O5 will improve the visible light photocatalytic activity of MoO3. 25 wt% V2O5 in MoO3 showed the highest efficiency and degraded Methyl orange, Rhodamine-B and Eosin Y completely in 30, 160 and 40 mints respectively, while Methylene blue is only partially degraded..
II. MATERIALS AND METHODS Samples of A.R grade MoO3, V2O5, Cu2O and TiO2 (Degusa P-25) as purchased are used in the photocatalytic studies.
Index Terms— MoO3, V2O5, Rhodamine-B, Methylene blue, Methyl orange, Eosin-Y, Photoctalysis
I.
A. Characterisation Techniques Phase purity of MoO3 was investigated with X-ray diffractometer (PANalytical- X’ Pert PRO, Japan) at room temperature, using Nickel filtered Cu-Kα radiation (λ= 1.54059 Å), with a scan rate of 2° min-1. UV–visible diffuse reflectance spectrum (UVDRS) of the sample was obtained with dry pressed disk samples using Shimadzu UV-visible spectrophotometer (UV-3600) between 200 to 800 nm range. Spectral grade BaSO4 was taken as reference in the UV-DRS.
INTRODUCTION
Semiconductor mediated photocatalytic oxidation of organic pollutants has attracted worldwide scientific research because of the ease of performance of reaction at ambient conditions exploiting the inexhaustible solar radiation that provides a cost effective clean technology. Among the binary metal oxide semiconductors, TiO2 is proved to be the most suitable photocatalyst for non-selective mineralization of several mutagenic/carcinogenic hazardous organic pollutants present in industrial waste water effluents. TiO2 is useful because it is inexpensive, photo stable, non-toxic, chemically inert and easy to synthesize.
B. Photocatalytic Studies 100 mg of catalyst powder was added into 100 ml Rh-B aqueous solution (5 mg/L). The suspension was magnetically stirred for 30 minutes in dark. The suspension was then exposed to 400 watts metal halide lamp; 5ml aliquots were pipetted at periodic time intervals and filtered through 0.45 micron Millipore filters to remove the suspended powder. Progress of decoloration was followed by recording the corresponding absorption spectra. The same procedure has been adopted for (10mg/L) MB, MO, Rh-B and EY dyes. All the experiments were conducted under ambient conditions. Extent of degradation of dye is calculated by using the expression.
However, major drawback of TiO2 is its relatively small absorption in the visible region due to its wide band gap of 3.2eV requiring U.V radiation of ˂ 380nm for excittion. Since U.V. radiation is ˂ 5% of solar radiation, intensive research efforts were focused to render TiO2 into a visible light active photocatalyst either through suitable doping, or addition of a sensitizer or by forming a nano/meso composite [1]. Alternately, photocatalysts from other binary metal oxides ZrO2 [2], MnO2 [3], NiO [4], Fe2O3 [5], ZnO [6], CO3O4 [7], WO3 [8], SnO2 [9], CdO [10], Bi2O3 [11], CeO2 [12], La2O3 [13] as well as mixed metal ternary oxides such as ZnWO4 [14], BiVO4 [15], Bi2MoO6 [16], Bi2WO6 [17], Bi2Mo3O12 [18], Fe2Mo3O12 [19] etc with band gap suitable for absorption in the visible region of solar radiation are also being explored. Recently, the authors reported a comparative study of visible light photocatalytic activities of MoO3, Cu2O and V2O5 against Degusa P25 [20]. The study revealed that photocatalytic activities of the above catalysts varied in the order TiO2˂MoO3˂Cu2O˂V2O5 for the degradation of
% degradation = (A0¯At)/A0 × 100 where A0 and At are respectively initial absorbance and absorbance at time‘t’
III. RESULTS AND DISCUSSION MoO3 is known to exist in three polymorphic forms-namely α (orthorhombic), β (monoclinic) and h (hexagonal). The sample used in the present study is orthorhombic as identified from its XRD pattern shown in Fig. 1.
T. Narasimha Murthy, Research Scholar, Dept. of Inorganic & Analytical Chemistry, Andhra University, Visakhapatnam-530 003, India P. Suresh, Research Scholar, Dept. of Inorganic & Analytical Chemistry, Andhra University, Visakhapatnam-530 003, India A.V. Prasada Rao, Professor, Dept. of Inorganic & Analytical Chemistry, Andhra University, Visakhapatnam-530 003, India
8
www.ijeas.org